1. Field of the Invention
The present invention relates generally to electronic monitoring equipment, and more particularly, to an improved ground conductor monitor and circuit breaker actuating device for detecting ground conductor faults in electrical power systems used with electrical mining equipment and other electrical equipment and for generating a trip command to actuate the power system circuit breakers. The preferred embodiment includes a fail safe design to prevent false tripping of the power system circuit breakers from spurious signals present in the pilot or ground conductors of the system as a result of stray DC signals, harmonic signals of the main power signal frequency or induced transients.
2. Description of the Prior Art
In electrical power systems used with mining equipment, it is essential that the power lines be properly grounded to prevent electrical charge buildup in the power system. Sparks caused by an electrical charge buildup in a particular machine or line due to faulty grounding may result in electrical shocks to operating personnel, ignition of volatile gases present in underground mines, or other accidents. Such accidents have potentially catastrophic results to personnel and the equipment.
Ground monitor devices have been developed in an effort to provide a detector for detecting loss of ground continuity in the electrical power system and for deenergizing the system before a hazardous condition develops. However, such monitors typically have the undesirable characteristic of responding to spurious signals commonly present in mining equipment electrical systems, and frequently deenergize the system when a ground fault has not actually occurred.